In an exhaust pipe of an internal combustion engine, there is provided an exhaust gas purifying apparatus that traps Particulate Matter (PM) contained in the exhaust gas. The exhaust gas purifying apparatus includes a particulate matter detection apparatus having a PM sensor to detect the quantity of particulate matter contained in the exhaust gas. Based on information obtained by the particulate matter detection apparatus, a failure detection of the exhaust gas purifying apparatus is performed.
The PM sensor employed in the particulate matter detection apparatus is configured so that for a time period from the completion of detection of particulate matter to the next detection, the PM sensor is heated to burn off the particulate matter having adhered to the PM sensor.
However, during a cold start of the internal combustion engine, condensate water, which is produced by the condensation of moisture in the exhaust gas, may adhere to the PM sensor. If the adhering timing of the condensate water coincides with the aforementioned heating timing of the PM sensor, water-induced cracking of the PM sensor may be caused. Therefore, in the particulate matter detection apparatus disclosed in Patent Document 1, for a predetermined time period during a cold start of the engine, heating of the PM sensor for burning off the particulate matter is not performed.